Juba, Sudan (CNN) -- Many Southern Sudanese on Saturday were jubilantly counting the moments to Sunday's historic referendum, a vote many hope will bring independence to their region, now a part of the nation of Sudan.

But reports of violence on Saturday in the south have left many observers and residents keeping their fingers crossed for what they hope is a peaceful voting period and a seamless transition to the formation of a new country.

Southern Sudanese people who lived in the north for decades were streaming into their homeland by river and land to vote in a referendum that observers say will favor independence.

Thabo Mbeki, the former South African president who is the chairman of the African Union High Level Implementation Panel on Sudan, told CNN there's a sense of optimism among Southern Sudanese ahead of the vote.

John Duku, a Southern Sudanese diplomat, said unity, or one undivided Sudanese nation, "means only one thing, it means war."

He said that "over the years unity has imposed war on us, the unity has imposed marginalization on us, the unity has imposed slavery on us. So, what is the meaning of unity. For the people of South Sudan it means only war."

Beginning Sunday, the black Christians and animists in the autonomous region of Southern Sudan will vote on whether to declare independence from the northern government dominated by Arab Muslims.

The two sides fought a war that killed some 2 million people from 1983 to 2005, when a peace treaty set the stage for the upcoming vote.

Mbeki said the tragic aspect of Sudanese history is that relations between the north and the south "have never been relations of equality," and that's the reason the country endured a long civil war.

He said that people in Sudan have to redefine and reconstruct the relations between the north and south after the referendum takes place.

Meanwhile, deadly skirmishes erupted along the north-south area involving Southern Sudan forces, the latest incidents along the disputed area in the past months and years.

Four rebel soldiers were killed and six captured in an attempted ambush on the forces, the Sudanese People's Liberation Army said in a statement Saturday.

Militias under the operation of rebel commander Galwak Gai led an ambush Saturday morning on SPLA soldiers in the border region's Unity State, but were repelled, according to the army.

The SPLA accused the rebels of trying to disrupt the referendum.

On Friday, the Sudan People's Liberation Army ambushed and captured 26 rebel troops in Mayom County of Unity State.

There has been fighting in the Abyei region, a contested border area and friction point in the north-south border region.

Wour Mijak, spokesman for the Sudan People's Liberation Movement in Abyei, said police on Friday intercepted militias of the nomadic Arab tribe, the Misseriya, and skirmishing ensued.

One police officer and four members of the militia were killed and six of the militia were injured.

Skirmishes continued Saturday, he said.

"This is a plan by the ruling National Congress Party to bring about the failure of the referendum in the south through the portal of Abyei," Mijak said, referring to the governing party of Sudan. The SPLM is the governing party of the southern region.

But Hamadi al-Dudu, a Misseriya tribal leader, said Misseriya herders were grazing their cattle in the area of Umbalayil and they were set upon by the Southern Sudanese forces in cars with heavy weaponry.

"It was an unprovoked attack. Our people fought back," al-Dudu said.

The south has repeatedly accused the north of trying to stoke tension by supporting rebels troops to destabilize the south, an allegation the Khartoum government denies.

The January 2005 Comprehensive Peace Agreement between the Sudanese government and the main rebel group in the south, the SPLM, called for the referendum.

It also envisioned a vote in Abyei, an oil-rich area that the British transferred to northern Sudan in 1905. The agreement says people in Abyei should vote on whether to remain part of the north or return to the south.

Both sides were to have worked out many details by now, but that has not happened, delaying the referendum in Abyei.

One unresolved issue involves who should vote: Should it be only members of the Ngok Dinka ethnic group, who tend to have more in common with southerners, or also the Misseriya, whose sympathies would most likely tilt toward the northern region?

CNN's David McKenzie and Ingrid Formanek in Juba and Nima Elbagir in Balom contributed to this report.